It is known to the art to prepare particles comprising different kinds of release systems in order to release active compounds or benefit agents at the right point in time to obtain the best possible use of the active components.
For many years it was common practice to make laundry, dishwashing or cleaning products available to consumers in the form of bulk-packaged products and to leave it to the consumer's discretion when using the product, to apportion the laundry, dishwashing or cleaning product to suit requirements specific to the application which were governed by the hardness of the water, the nature, amount and/or degree of soiling of the clothes, dishes etc. to be washed or articles to be cleaned, the amount of liquid in the laundry, dishwashing or cleaning bath, or other parameters.
In view of consumers' desire to obtain laundry, dishwashing or cleaning products that could be apportioned more easily and conveniently, these products have increasingly been made available in a form rendering individual apportionment superfluous: laundry, dishwashing or cleaning products have been made up in measured portions containing all the constituents needed for a laundry, dishwashing or cleaning cycle. In the case of solid products, such portions have frequently been formed into shapes (sometimes containing more than one phase), such as pellets, beads, tablets (“tabs”), blocks, briquettes, etc., which are introduced into the wash liquor as intact products. It has also been proposed to enclose liquid products in water-soluble capsules that dissolve upon contact with the aqueous bath and release their contents into the bath.
One drawback for some of these products is that all the constituents needed in the course of a laundry, dishwashing or cleaning cycle enter the water bath at the same time. Not only does this create problems of incompatibility of certain constituents of a laundry, dishwashing or cleaning product with other constituents, but also it becomes impossible to selectively introduce specific constituents into the bath at a defined point in time. Another drawback is that even if a delayed release mechanism is incorporated in the solutions then it is not very effective and it is difficult to provide a desired release profile.
In the state of the art, means have more recently been described whereby individual laundry, dishwashing or cleaning product constituents can be selectively apportioned at a defined point in time during their application. For example, temperature-controlled release of active ingredients has been described, allowing active substances like surface-active agents, bleaching agents, soil release polymers and the like to be released in the main wash, or cleaning cycle, or even in a post treatment cycle, e.g. in the final rinse in the case of machine dishwashing.
The use of paraffin waxes with a melting point above 50° C. has been described on a number of occasions. One product on the market uses a paraffin wax core as a carrier or matrix in a dishwashing tablet, in order that a final-rinse surface-active agent (“rinse aid”) incorporated therein does not get released during the cleaning cycle and is not released until the final rinse cycle of a dishwashing machine. If released too soon, for example during the cleaning cycle, the final-rinse surface-active agent will for the most part be pumped away in the intermediate rinse and will then yield little or no effect in the final rinse. Adoption of a matrix material with a melting point at the temperature of the final rinse cycle ensures that the final-rinse surface-active agent emulsified in the matrix (or, ideally, in molecular dispersion in the matrix) stays enclosed in the matrix during the cleaning cycle, which is run at temperatures of up to 55° C., and is not released until the matrix material melts in the final rinse cycle in which temperatures of up to about 65° C. are attained.
This solution for protecting the final-rinse surface-active agent has proved effective in practice. One drawback, however, is that the amount of matrix material in a dishwashing tablet core consisting of paraffin wax and final-rinse surface-active agent accounts for between 30 and 95% of the total mass of the core, typically approx. 50% of the total mass. The matrix material, especially in this quantity, may leave residues on the cleaned articles, e.g. on crockery or glassware, and moreover may interfere with the action of the final-rinse surface-active agent which it contains and which is released when the paraffin wax melts. One reason for this could be that the final-rinse surface-active agent remains bonded to the boundary surface between the lipophilic carrier material and the rinse bath after the paraffin wax has melted, and therefore fails to yield the desired effect.
Another drawback of temperature-controlled release of active ingredients in laundry or dishwashing products is that typical domestic laundry and dishwashing machines have quite a large number of programs that differ significantly, particularly in their temperature and time profiles. For example, the programs most commonly adopted in modern dishwashing machines have peak temperatures in the cleaning cycle of 50 to 60° C. or 60 to 70° C.; the precise temperature level can vary depending on the manufacturer and the type of machine.
WO 01/44434 (Henkel) relates to combinations of physico-chemical triggers with enzyme triggers which results in perforation of particles due to enzyme activity in the wash solution. However, certain drawbacks are seen in having the enzymes in the wash water; this technology necessitate that the detergent comprises the required enzymes to perforate the particle. The detergent needs to be formulated in a way which is non-hostile to the enzymes. Moreover, it is difficult to ensure the right enzyme activity in the detergent to guarantee release of the payload at the right time in the wash process.
WO 9937746 (Procter & Gamble) relates to a multi-layer detergent tablet comprising a core, a first encapsulating layer comprising a detergent active, and a second encapsulating layer comprising a disruption system, which leads to delayed release of the detergent active.
EP-A-971 024 (Procter & Gamble) discloses laundry cleaning compositions comprising a detersive ingredient and a product of the reaction between a primary amine and a perfume component. It is described that the active component is released over a longer period than when it is used on its own.
The following documents disclose other examples of particles for use in detergents: US 2003/0191043, US 2005/003980, WO 99/29820, WO 97/22680, EP 1 388 585, EP 304332, EP 458845, U.S. Pat. No. 5,733,763.